Memories formed with inorganic semiconductor elements such as silicon have high reliability, low manufacturing cost, and a wide variety of applications, and thus are widely known in general.
Development of novel memories in which inorganic semiconductor elements using silicon or the like, insulating films, and/or wirings are formed over a flexible substrate with use of conventional materials and processes has been actively made.
Memories that are formed on a flexible substrate such as plastics can be embedded in paper, and are considered to be used as name cards, posters or the like for information exchange.
In a development of a one time programmable (OTP) memory, that is, a memory that can write data by breakage of an insulating film and short circuiting between wirings in data writing, when a semiconductor element is formed over a flexible substrate, a manufacturing process and operation of such a one time programmable (OTP) memory are comparatively easy in some cases.
In a memory cell of an anti-fuse type memory, an assist capacitor is disposed to increase writing ability. In a conventional memory, an assist capacitor and a memory element are independently disposed.
An assist capacitor will be described. In parallel writing with an element, a capacitor for supplying charges to the element (hereinafter, referred to as an assist capacitor) is provided so that high yield in writing can be realized. Examples of the assist capacitors include ones including MOS capacitors, which are each formed from “active layer-GI film-metal film”, and ones including MIM (Metal-Insulator-Metal) capacitors, which are each formed from “metal film-insulating film-metal film”
[Patent Document 1] Japanese Published Patent Application No. H02-023653